Drug Interactions between digoxin and fingolimod

MONITOR CLOSELY: The risk of severe bradycardia and atrioventricular (AV) block may be increased during initiation of fingolimod treatment in patients receiving other drugs that slow heart rate or AV conduction such as beta-blockers, certain calcium channel blockers (e.g., diltiazem, verapamil), and digitalis. Fingolimod can cause a decrease in heart rate during initiation of therapy that is apparent within an hour of the first dose and maximal at approximately 6 hours postdose in most cases, but occasionally up to 20 hours after the first dose. Further, but smaller decreases in heart rate may occur after the second dose, although heart rate eventually returns to baseline within one month of chronic treatment. The mean decrease in heart rate in patients receiving fingolimod 0.5 mg at 6 hours after the first dose was approximately 13 beats per minute (bpm). Heart rates below 40 bpm were rarely observed. In controlled clinical trials, adverse reactions of symptomatic bradycardia (hypotension, dizziness, fatigue, palpitations, chest pain) following the first dose were reported in 0.5% of patients receiving fingolimod 0.5 mg, compared to no patient on placebo. Initiation of fingolimod treatment has also resulted in transient AV conduction delays. First- and second-degree AV block (prolonged PR interval on ECG) following the first dose were each reported in 0.1% of patients receiving fingolimod 0.5 mg, compared to no patient on placebo. In a study of 698 patients with available 24-hour Holter monitoring data after their first dose, second degree AV blocks, usually Mobitz type I (Wenckebach), were reported in 3.7% of patients receiving fingolimod 0.5 mg and 2% of patients receiving placebo. Bradycardia and conduction abnormalities were usually transient and asymptomatic, and resolved within the first 24 hours on treatment, but they occasionally required treatment with atropine or isoproterenol.

MANAGEMENT: Fingolimod has not been adequately studied in patients receiving beta-blockers, calcium channel blockers, or digitalis. The possibility of switching to alternative agents that do not slow heart rate or AV conduction should be evaluated by the physician before initiating fingolimod. In patients who cannot switch, overnight continuous ECG monitoring after the first dose is recommended in accordance with the product labeling. The same precautions are applicable if, after the first month of treatment, fingolimod is discontinued for more than two weeks and then restarted, since the effects on heart rate and AV conduction may recur on reintroduction of fingolimod. Within the first 2 weeks of treatment, first-dose procedures are also recommended after interruption of one day or more; during week 3 and 4 of treatment, first-dose procedures are recommended after treatment interruption of more than 7 days. The first dose should always be administered in a setting where resources to appropriately manage symptomatic bradycardia are available.